Post on 14-Mar-2020
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Content Introduction
LET Market Status
C-RAN overview
C-RAN Benefits and Features
Benefits: Installation/Evolution/Performance Aspects
Features: Centralized Coordination, Inter-site Operation
C-RAN Architecture
DU-RU Function Split
Fronthaul Technology
Future Evolution
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Soaring LTE Compare to 3G
(Source : WCIS, Informa Jan 2014)
Dec 2009 Dec 2012 Dec 2014 (E) Dec 2013 Dec 2010 Dec 2011 LTE
Oct 2001 Oct 2002 Oct 2003 Oct 2004 Oct 2005 Oct 2006
2007
263 Commercial operators in 97
countries
41 million subs added in Q4 2013
3
LTE Expansion in Korea
13
Smart Cache™
3G
22
VoLTE CA
Multi Carrier
LTE Launch
Wideband LTE
eMBMS C-RAN
8
6 Carrier 6 Sector
4
World Firsts in Korea
4.9M Subscribers
300Mbps
Jan. 2014 Commercial
5
LTE Traffic Usage in Korea
2.5 GB
30.9 PB
43.3 PB
50 PB
58.4 PB
68.4 PB 72.7 PB
79.8 PB
86.9 PB
1.8 GB
2.8 GB
Traffic usage per subscriber
Total traffic usage
~50% Growth in LTE traffic per user in just over 1 year
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Mobile TV in Korea
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Mobile TV in Korea
(Paid Subs.)
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Mobile Traffic Explosion
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Macro cells Small cells
Mobile Traffic Explosion
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Centralized Baseband Processing
Cloud Computing
Coordinated Radio
Clean Radio Access Network
4C in C-RAN
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Network Evolution
Traditional BS (DU/RU in one box)
Distributed RAN (D-RAN)
(DU/RU in different box )
Centralized RAN (C-RAN)
(DU Cloud + Remote RU)
DU
DU Cloud
RU
DU
Server
RU
* DU: Digital Unit * RU: Radio Unit
DU
RU
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C-RAN Network Diagram
Distance < 20 km
Active Optic MUX
Passive Optic MUX
Active WDM
Passive WDM
Fronthaul Network (Optical Transport
Network)
* WDM : Wavelength Division Multiplexing * RRU: Remote Radio Unit
DU Centralized Site Remote Site
(Baseband Processing, Coordinator, Edge App.)
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C-RAN in Seoul (1/2)
※ Seoul covers 600Km2, 10M pops
Central Site
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C-RAN in Seoul (2/2)
Optic MUX
DU Centralized Site
Remote Site
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Installation Aspect
C-RAN
Total N Site - N BBU - Nx3 RRU
Distributed-RAN
Total N Site - Nx3 RRU 1 C-RAN BBU
C-RAN BBU
RRU RRU RRU
BBU
RRU RRU RRU
BBU
RRU RRU RRU
BBU
RRU RRU RRU
RRU RRU RRU
RRU RRU RRU
Centralized-RAN
* DU: Digital Unit * BBU: Base Band Unit * RRU: Remote Radio Unit
Reduced CAPEX/OPEX, CO2
Simpler site installation
Reduced site rental and electricity cost
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Evolution Aspect
Site visiting - Change Tech-A BBU to Tech-B BBU
Central office visiting - Change Tech-A Card to Tech-B Card
Tech-B card
Tech-B C-RAN Tech-A
C-RAN
Easier evolution with new h/w, new technology
• e.g. BBU + IT server
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Performance Aspect
Wireless Channel Information
Scheduling info. (QoS/CQI/Load)
IP Network
Radio Resource Coordination Enhanced Performance
Information exchange over IP network - Long Latency, Low Speed
Information exchange side the Rack - Short Latency, High Speed
Distributed-RAN Centralized-RAN
C-RAN
* QoS: Quality of Service * CQI: Channel Quality Information
Easier evolution for better performance with new h/w, new technology (e.g. BBU + IT server)
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C-RAN Coordination (1/3)
Optimal resource allocation over multi-cell network
in a centralized manner
Cell#3
Cell#1
Cell#2
Cell#N
Cell#4
UE A
UE B
UE D
Cell#1 Cell#2 Cell#3
Cell#4 Cell#5 Cell#6
Cell#7 Cell#8 Cell#9
Cell#N-1 Cell#N
UE B UE A
UE C
UE D
Channel/Scheduling Info.
(QoS/CQI/Load)
Resource Coordination
C-RAN Coordinator
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C-RAN Coordination (2/3)
Cells cooperate with each other in a distributive way. (Each cell decides its own air resource usage.)
To increase the system efficiency in long-term average sense
Limited information (specified in the standard interface) is shared among cells.
Cells are coordinated in a centralized way. (Central coordinator decides the whole network air resource coordination.)
To increase the system efficiency at every millisecond
More information (than standard interface) is exchanged with central coordinator.
ICIC C-RAN Coordination
Interference
X2 Load Information
Interference
Channel Info.
Scheduling Info.
C-RAN Coordinator
Coordination Output
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C-RAN Coordination (3/3)
Serving
Nbr 2
VoLTE VoLTE VoLTE
Serving Cell
Nbr 1
VoLTE UE
VoLTE is affected by neighbor cell interference
Nbr 1
Nbr 2
Serving
Nbr 2
VoLTE
blank
VoLTE
blank
VoLTE
blank
Serving Cell
Nbr 1
VoLTE UE
Interference avoidance by blanking
Nbr 1 blank blank blank
Nbr 2
Intf., Intf.
Intf. Intf.
VoLTE Example Voice quality improvement at cell edge
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UL CoMP Joint Reception (JR)
Uplink signal is jointly received at multiple points to improve the received signal quality
Conventional UL CoMP JR
UL signal path used by serving cell
*UL CoMP: UpLink Coordinated Multi-Point
SINR
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Inter-site Carrier Aggregation (1/2)
Carrier aggregation using cells from different sites
Chooses Pcell and Scell with the best signal quality
Seamless CA in coverage mismatch area
* Pcell: Primary cell * Scell: Secondary cell
without CA
Thro
ugh
pu
t
이동구간 Coverage mismatch area
with CA
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Inter-site Carrier Aggregation (2/2)
Select and aggregate the best cell of each carrier
22.3 Mbps 45.9 Mbps
1.8 GHz
800 MHz
Cell 0 Cell 1 1.8 GHz 800 MHz
Cell 0 Cell 1
Conventional CA Inter-site CA
(Best Cell Aggregation)
1.8 GHz cell coverage
800 MHz cell coverage
1.8 GHz cell coverage
800 MHz cell coverage
PCell 8.3dB(15.6M) 1.6dB(7.5M)
SCell -1.4dB(6.7M) 12.8dB(30.3M)
8.3dB(15.6M) 1.6dB(7.5M)
-1.4dB(6.7M) 12.8dB(30.3M)
*Based on actual measurement in Korea (FDD, 10 MHz + 10 MHz)
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HetNet Carrier Aggregation
CA between Macro and Small cells
Control and voice are supported by Macro cell
No handover
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One cell operation
Same PCID for multiple N cells
No handover among N cells with same PCID
C-RAN supports larger and flexible N
C
A B
A B C
SIN
R
One Cell operation
Conventional
Small cell
Small cell
One Cell Operation
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C-RAN Benefits and Pitfalls
CAPEX/OPEX Savings
Multiple sites share a high-density DU
Small form factor for each site
Fewer visits to sites for maintenance
EPC
Traditional RAN C-RAN
EPC Backhaul Network
Fronthaul Network Backhaul
Network
Transport Cost between DU/RU
Current technology requires dark fibers
because of high bandwidth
Additional central offices required
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Consideration for C-RAN (1/2)
To minimize transport cost between DU and RU
Minimization of the bandwidth
Alternative transport solutions (e.g. Microwave, Ethernet)
To maximize resource pooling
High density DU, and DU pooling
Reuse for evolved radio technology
To maximize radio performance
Edge performance enhancement by inter-site operation
High-bandwidth and low-latency connectivity between DUs
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Consideration for C-RAN (2/2)
To maximize Maintenance Efficiency
Plug and Play RU
Automatic re-parenting between DU and RU
To utilize the benefits of DU centralization
Interworking with Coordination server, Cache server, Local breakout
server, Analytics server, etc.
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Since March 2013,
Study of C-RAN Technologies
• Function Split between DU and RU
• DU pooling
• Virtualization
• RAN Sharing
• Prototype Development * DU: Digital Unit * RU: Radio Unit * RAN: Radio Access Network
NGMN Project C-RAN
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DU-RU Function Split
(Source: NGMN RAN Evolution C-RAN white paper )
* IV : CPRI interface * IV’ : Compressed CPRI interface
Function Split Options Delay
Sensitivity Bandwidth
Level Comment
Partial L1 at site, L1/L2/L3 centralized
High High • CRAN features applicable
L1 at site, L2/L3 centralized
High Medium • CRAN features not applicable
L1/L2 at site, L3 centralized
Medium Low • CRAN features not applicable • Less centralization effect
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DU-RU Architecture
Option C Option A
DU
RF
RU PHY
Layer 3 Layer 3 PDCP
Layer 3 Layer 3 RLC
Layer 3 Layer 3 MAC
Layer 3 Layer 3 PDCP DU
RF RU
Layer 3 Layer 3 RLC
Layer 3 Layer 3 MAC
Layer 3 Layer 3 PHY
DU
PHY (Cell Processing)
Front- end
RF RU
Layer 3 Layer 3 PDCP
Layer 3 Layer 3 RLC
Layer 3 Layer 3 MAC
Layer 3 Layer 3 PHY
(User Processing)
Option B
DU processing by IT server (Workload is proportional to user traffic amount)
Much smaller bandwidth b/w DU and RU. Limited C-RAN features support.
Conventional
(Source: NGMN RAN Evolution C-RAN white paper )
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Fronthaul Network Topology
CO
T
RT
RT
RT
RT
RT
RT
RT
RT
CO
T
Point-to-Point Topology (A operator who owns abundant dark fibers)
Ring Topology (B operator who wants to reduce dark fiber rental)
* COT : Central Office Terminal * RT : Remote Terminal
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DU-RU Interface: CPRI
CPRI protocol layers
* CPRI : Common Public Radio Interface
LTE 20MHz 4x4 MIMO requires 5Gbps
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Concept of CPRI Compression (1/2)
…0010101111010101 Compression Decompression
Reduced-rate IQ data (DL)
Compression Decompression 0010101111010101…
Reduced-rate IQ data (UL)
Compression/Decompression algorithm is applied to both ends
Baseband Processing Remote Radio Unit
Optic Cable I/Q Sample I/Q Sample
Compression for DL Decompression for UL
Compression for UL Decompression for DL
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Concept of CPRI Compression (2/2)
* D. Samardzija et al., “Compressed Transport of Baseband Signals in Radio Access Networks”, IEEE Trans. Wireless Comm., Sep. 2012
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Effect of CPRI Compression
Before After
Reduced Bandwidth between DU and RU
Number of optic link and optic module is reduced
10G x 2 10G x 1
* COT : Central Office Terminal * RT : Remote Terminal
2.5G x 8
RT
2.5G x 4 2.5G x 4 2.5G x 8
RT RT
COT RT
RT RT
COT
Example: compression ratio of 2:1
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CPRI over Ethernet
Ethernet Fronthaul
Ethernet based DU-RU Networking
Automatic re-parenting between DU and RU
Dynamic DU pooling
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Analog Signal over Microwave
CPRI to Analog over Microwave
Limited distance
Graceful performance degradation
core
network EPC M/W
UDC CPRI
RU
central unit (cluster)
PDCP
RLC MAC PHY CPRI RF
M/W
UDC
BWOptimized
150MHz
BCPRI 4915.2Mbps
(20MHz, 4x4 MIMO)
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5G and C-RAN
5G not standardized yet
mmWave(eg. 28GHz) and very broad bandwidth(800MHz~1GHze)
Lots of antennas (e.g. 64)
UE peak throughput of 1Gbps ~ 1.5Gbps
Providing services in hot spots due to short coverage
C-RAN for 5G
CPRI fronthaul may not be feasible due to very high sampling rate.
Function split needs to be further investigated.
Higher bandwidth between DUs is required.
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Cloud based Services
Fronthaul Network
More intelligent processing by Cloud Server
Radio performance enhancement by scheduler and SON processing
Cache / Local Breakout / Analytics / M2M / Etc.
Intelligent Processing
* SON : Self Organizing Network * M2M : Machine to Machine